1. Field of the Invention
The present invention relates to a technology for positioning a disk type storage media, and more particularly, to a circuit for generating a tracking error signal.
2. Description of the Related Art
Due to the prompt development the optical technology, the storage capacity of the optical storage media is becoming larger and larger. Relatively, the track number of optical storage media is becoming more and more. Therefore, to develop the technique for positioning the track is becoming more and more important.
FIG. 1 is a diagram of a conventional method for tracking. Referring to FIG. 1, the label 11 is represented to a position of a pick-up head of an optical disk drive. The pick-up head 11 can be divided into four areas, i.e. A, B, C and D, on the irradiation area of the optical disk. The tracks of the optical storage media include the land tracks and groove tracks. The tracking error signal in prior art can be calculated by the following equation:TE=φ(IA+IC)−φ(IB+ID)
The IA, IB, IC and ID are pick-up signals and respectively represent intensities detected by light detecting elements A, B, C and D.
FIG. 2 illustrates a block diagram of circuit for generating a tracking error signal published by European Computer Manufactures Association (EMCA). Referring to FIG. 2, the circuit includes a pick-up head 201 with 4 light detecting element, two adding amplifiers 202 and 203, two equalizers 204 and 205, two comparators 206 and 207, a phase comparator 208, two low-pass filters 209 and 210 and a differential amplifier 211. The adding amplifier 202 will add the pick-up signals IA and IC to obtain a (IA+IC) signal, and the adding amplifier 203 will add the pick-up signals IB and ID to obtain a (IB+ID) signal. Because the high frequency component of (IA+IC) and (IB+ID) signals are weak, the equalizers 204 and 205 will respectively amplify the high frequency component of the (IA+IC) and (IB+ID) signals. The tracking error signal is generated by the process of the comparators 206 and 207, the phase comparator 208, the low-pass filters 209 and 210 and the differential amplifier 211.
There are some improvements for improving the abovementioned standard circuit of EMCA, such as U.S. Pat. No. 5,258,968, U.S. Pat. No. 6,137,755, U.S. Pat. No. 7,345,963 and U.S. Pat. No. 7,345,964. However, those patents submitted by the above do not disclose how to improve or simplify the equalizer. Since the equalizer and the pre-stage analog circuit thereof occupy a lot of layout area in the integrated circuit (IC), so that the layout area of the IC will be increased a lot, furthermore the cost of product with such IC will be increased and the competitiveness thereof will also be decreased.